Reduction of isoflurane MAC with buprenorphine and morphine in rats

Abstract

Preoperative analgesics are being increasingly used to provide analgesia in the intraoperative and postoperative period. Opioids reduce anaesthetic requirements, although the effect varies with the different drug and species. The aim of this work was to determine whether buprenorphine reduces the minimum alveolar concentration (MAC) of isoflurane in a dose-related fashion, and whether this effect is similar to morphine when clinical doses of both drugs are used in the rat. Thirty-six male Wistar rats were anaesthetized with isoflurane, and MAC was determined before and after the administration of either buprenorphine or morphine. MAC of isoflurane was determined from alveolar gas samples when a standard noxious stimulus, in the form of a tail clamp, was applied. The duration and degree of reduction of the MAC of isoflurane were recorded. Basic cardiovascular and respiratory measurements were also recorded. Buprenorphine (10, 30 and 100 microg/kg) and morphine (1, 3 and 10 mg/kg) reduced in a dose-dependent fashion the MAC of isoflurane by 15%, 30% and 50%, respectively. Buprenorphine resulted in less cardiovascular and respiratory depression and had a longer-lasting action than morphine. In conclusion, buprenorphine has a dose-related isoflurane sparing effect in the rat similar to that caused by morphine at clinical doses of both drugs.

Involvement of GABA and opioid peptide receptors in sevoflurane-induced antinociception in rat spinal cord

“…The C-fiber-induced response recorded in the peripheral nerve or muscle is commonly used to characterize spinal processing and is considered to be an acute pain model [11] . By means of this model, the present work for the first time shows that inhalation of sevoflurane produces a dose-dependent reduction of primary sensory afferent C-fiber-mediated nociceptive responses in the rat after transection of the spinal cord at T [9][10] . This indicates that sevoflurane not only suppresses excitation in α-motor neurons but also inhibits the activity of painsensitive neurons in the dorsal horn of the spinal cord, in the absence of supraspinal input.…”

“…It has been reported that intravenous or intrathecal morphine is able to reduce the minimum alveolar concentration of halothane [8][9][10] . In the present study, the fact that naloxone blocked the sevoflurane-induced inhibition of nociceptive C responses provides further support for the involvement of spinal opioid receptors in antinociception mediated by sevoflurane.…”

“…For example, a common property of a wide spectrum of general anesthetics, including barbiturates and propofol, is enhancement of the action of GABA A receptors [1][2][3][4] . Increasing evidence have indicated that the spinal cord is pivotal in the immobility induced by volatile anesthetics because the anesthetics depress the activity of α-motoneurons in the spinal cord [5,6] , in which process spinal GABA receptors and opioid peptide receptors may be involved [7][8][9][10] . However, there has been few study on the effects of sevoflurane on pain processing in the spinal cord.…”

Three-dimensional optoacoustic imaging as a new noninvasive technique to study long-term biodistribution of optical contrast agents in small animal models

“…19,34 Compared to halothane, isoflurane causes less functional complications, such as the depression of cardiopulmonary function. 40 Also, isoflurane reduces renal blood flow, glomerular filtration rate, and urinary flow. It is not a significant hepatotoxin.…”

Isoflurane with morphine is a suitable anaesthetic regimen for embryo transfer in the production of transgenic rats

“…An additional advantage of opioid analgesics that is not exploited fully by our iso urane/ morphine regimen is the ability of these agents to substantially reduce the iso urane level required to achieve a surgical depth of anaesthesia. Morphine (dosed at 3 mg/kg) lowers the minimum alveolar concentration (MAC) of iso urane by 30% (Criado et al 2000), suggesting that the iso urane concentration needed to maintain anaesthesia could be reduced to 1.4%. Another potential improvement to our iso urane regimen could be achieved by utilizing a noncontrolled analgesic agent instead of an opioid, thereby saving the time required to complete regulatory paperwork mandated for the use of controlled analgesic agents.…”